方法一，使用通知：

1、新增監聽

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(volumeDidChange:)name:@"AVSystemController_SystemVolumeDidChangeNotification" object:nil];
[[UIApplication sharedApplication] beginReceivingRemoteControlEvents];

2、新增執行方法

- (void)volumeDidChange:(NSNotification *)notification

{

    DDLogInfo(@"%@-%@，點選音量鍵靜音", THIS_FILE, THIS_METHOD);

}

3、銷燬的時候，移除監聽

[[NSNotificationCenter defaultCenter] removeObserver:self name:@"AVSystemController_SystemVolumeDidChangeNotification" object:nil];

 [[UIApplication sharedApplication] endReceivingRemoteControlEvents];

方法二，使用KVO：

1、新增KVO

[[AVAudioSession sharedInstance] addObserver:self forKeyPath:@"outputVolume" options:NSKeyValueObservingOptionNew | NSKeyValueObservingOptionOld context:(void *)[AVAudioSession sharedInstance]];
 

2、實現方法

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context{
    if(context == (__bridge void *)[AVAudioSession sharedInstance]){
        float newValue = [[change objectForKey:@"new"] floatValue];
        float oldValue = [[change objectForKey:@"old"] floatValue];
        // TODO: 這裡實現你的邏輯程式碼
    }
}

3、銷燬的時候，移除KVO

[[AVAudioSession sharedInstance] removeObserver:self forKeyPath:@"outputVolume" context:(void *)[AVAudioSession sharedInstance]];

鎖屏監聽音量鍵：

https://blog.csdn.net/qq_450351763/article/details/54135615